Isolated Ninespine stickleback population, Pungitius pungitius (L.), in northeast Finland: large fish with reduced pelvis

摘要

Gasterosteidae fish species are well known for their variability of intra-species morphology (NELSON 1971, ZYUGANOV 1989, BLOUW & BOYD 1992). Nine-spine stickleback (Pungitius pungitius (L.)), usually reaches 50-60 mm in length (BERG 1949) and "probably never exceeds 10cm" (WOOTTON 1976). Its populations can differ in morphology characterized by the absence of spines and reduction of pelvis, depending on the predation pressure in the community (BLOUW & BOYD 1992, ZIUGANOV & ZOTIN 1995). BLOUW & BOYD (1992) have shown these phenomena, especially the spine deficiency, to be heritable; absence and asymmetry of spines are highly heritable, but the bony pelvic vestiges of spineless fish not. This study dealt with the Ninespine stickleback population in hard water Rytilampi pond (66°23′03″N, 29°19′12″E) in the Oulanka National Park, Finland. The sticklebacks, caught for parasite-logical purpose, attracted attention by their large size (up to 105 mm; later an angler caught 110 mm long fish). The lack of pelvic spines was observed, and the dissection of pelvis revealed an asymmetrical reduction of bones. Here, age-length relationships of Ninespine stickleback of Rytilampi were compared to two other local populations and to some other published results. Also the various types of reduced pelvic bones and their asymmetry were described.